Although a large volume of literature focuses on the outcome of extremely low birthweight (ELBW) infants, data are not available which clearly define the prevalence of handicapping conditions in this population during infancy or childhood. While it is apparent that mortality rates have declined dramatically over the past 20 years in this group of infants, it is not clear that morbidity has been similarly affected. Accurate information concerning outcome of ELBW infants is essential when cost versus benefit discussions arise because of the tremendous resources utilized in the care of the ELBW infants. Specific study objectives include the determination of 18 months (corrected age) of: mortality and the prevalence of specific medical morbidities; developmental characteristics of motor skills, cognitive skills, language and behavior using standardized methods; growth outcome and its relationship to developmental outcome; significant family stress in this population and its relationship to family integrity as well as compliance with medical and developmental care; utilization of special support services and early intervention programs.